Detonators are used for various purposes, both military and civilian ones, but will here be described mainly in relation to applications for commercial rock blasting where typically a plurality of detonators from an assortment with different internal time delays are connected in a network of electric or non-electric signal conductors.
In such detonators pyrotechnical charges may be used for different purposes in a pyrotechnical train converting an ignition pulse from igniting or signaling means to a detonation in a base charge, e.g. as a rapid transfer or amplifying charge, a slower delay charge, a gas-impermeable sealing charge or an ignition charge for detonating said base charge.
One example of a pyrotechnical charge in a pyrotechnical train is given in U.S. Pat. No. 2,185,371, which discloses a delay charge with an alloy of antimony as a specific fuel. Other examples are given in GB-A-2 146 014 and DE-A-2 413 093, which disclose a pyrotechnic fuel composition for severing conduits and an explosive mixture, respectively. As an example of a method of producing pyrotechnical charges reference is made to EP 0 310 580, which discloses the production of delay and ignition charges.
Common to all this prior art is, however, that it does not disclose or even suggest the use of our specific ignition charge to quantitatively and reliably detonate secondary explosive charges.
Ever increasing demands are placed on all the parts of the pyrotechnical train. A main requirement is that the charges shall burn with well defined and stable reaction rates with limited time scatter. The burning rate must not be significantly influenced by ambient conditions or ageing. The charges shall have reproducible ignition properties but yet be insensitive to shock, vibrations, friction and electric discharges. The nominal burning rate should be adjustable with minor charge modifications. The charge mixture has to be easy and safe to prepare, dose and press and not too sensitive to production conditions. In addition thereto there is a growing requirement that the charges must not contain toxic substances and that preparations can be made without health hazardous conditions such as use of solvents.
Although pyrotechnical charges in general can be regarded as mixtures of a fuel and an oxidant, and accordingly many compositions should be potentially available, the above described requirements together significantly limit the choice of suitable compositions for each of said charges. A need exists, however, for further improvements, both in respect of performance and because hitherto established compounds for the purpose, such as lead or cromate compounds, are becoming less available and accepted.